A clutch assembly generally comprises at least one clutch and at least one activation unit for activating the clutch. The clutch usually comprises a housing, at least one sump, at least one disk carrier and a multiplicity of clutch disks which run in the housing in a (cooling) medium, in particular oil. In this context, the clutch disks at least indirectly exchange heat with the medium. The clutch is heated decisively by the frictional power which is input into the clutch and which is generated on the basis of differences in rotational speed of disks which rotate relative to one another and rub against one another. This heat must be discharged again from the clutch, wherein the medium is mounted at least partially in the sump, fed to the clutch disks and then fed again to the sump (cooling circuit).
The transmitted torque of such a disk clutch is very dependent on the temperature or the heating of the disks. Owing to the stringent requirements which are made of the positional accuracy of a disk clutch, this temperature influence must be taken into account during the operation of the disk clutch. For example an electronic control unit which is assigned to the clutch can be configured and determined to detect this temperature influence and compensate it virtually completely. However, in order to be able to compensate this influence correspondingly, the disk temperature which is present in the clutch must be known as precisely as possible.
Since the direct integration of temperature sensors in the disk pack is too costly and susceptible to faults, the disk temperature could be estimated by means of corresponding temperature models which run in the electronic unit. For this purpose, static temperature models are required which are based on sensory detection or direct measurement of the temperature of the medium.
Such static temperature models are, however, too imprecise to take into account the dynamic influences of operating-point-dependent cooling. Since the flow of the medium through the clutch usually depends on the operating point of the clutch, an operating-point-specific cooling behavior of the clutch disks, which cannot be described by means of known static temperature models, is produced. In addition, the sensory measurement of the temperature of the medium is very costly and susceptible to faults, wherein measurement of the temperature directly in the region of the clutch disks, such as would be necessary for the sensory detection of operating-point-dependent cooling, is also impossible to implement with acceptable expenditure in terms of sensors.